The main criteria are that you have a degree and a passport from a native-English speaking country.
See job adverts on eslcafe and tefl.com

Some schools will have 'secret' other criteria; like they want you to be white, so you look good in school publicity photos; or they want you to have a certain accent (American, not New Zealander, or something); or they want you to BE a native speaker, not just have native-level ability.

But not all schools have that criteria, so you should still apply. Though the more 'proof' you have of your ability om English (e.g., a CELTA, a degree from an English-speaking country), the fewer questions you'll likely get.